Method of manufacturing bismuth shot

ABSTRACT

A molten metal alloy, such as bismuth and tin, is injected into a die block to form a tightly packed rectangular array of shot pellets. The ratio of waste sprue to shot pellets is minimized and the shot pellet yield per casting is maximized by allowing the shot pellets in the rectangular shot array to touch other shot pellets in adjoining rows and columns through small interconnecting vias. The interconnecting vias allows the molten metal to flow between shot pellets, as well as from the sprue into the shot pellets. This allows the molten metal to bypass blockages that reduce the shot pellet count per casting. The flow of the molten metal through the die block is also improved by machining away a small amount of metal from the face of the die in order to form a flashing between the shot pellets.

BACKGROUND

[0001] In recent years there has been an increase in the demand for anon-toxic replacement for the traditional lead shot pellets used inshotguns. The use of toxic lead shot by hunters leads to the poisoningof many natural habitats, particularly the lakes and ponds where ducks,geese and other waterfowl are found. Presently, the only approvedalternatives to lead shot are steel shot and bismuth-tin alloy, whichare not toxic like lead. Unfortunately, steel shot has significantdrawbacks compared to lead shot. Steel shot is much less dense than leadshot and therefore slows down much more rapidly than lead shot whenfired. This makes hunting with steel shot less accurate because huntersmust “lead” a moving target by a greater amount when using steel shot.Furthermore, because steel shot is so much lighter than lead shot, itcauses far less shock and injury to the hunter's quarry. Rather thandying quickly after impact, the wounded animal will frequently run orfly a great distance before bleeding to death. Additionally, steel shotis more damaging to shotgun barrels because steel is harder than lead.

[0002] A more suitable replacement for lead is bismuth shot, inparticular bismuth alloy shot. Bismuth may be alloyed with other metals,such as tin, to thereby produce bismuth alloy shot that is very nearlythe same density as lead. Bismuth alloys are soft like lead andnon-toxic. For these reasons, bismuth alloy shot does not damage shotgunbarrels the way steel shot does and, because of its comparable density,has the accuracy and killing power of lead shot.

[0003] U.S. Pat. No. 4,949,644 to Brown discloses a non-toxic wildlifeshot pellet for use in shotgun shells that is formed from bismuth orbismuth alloys. U.S. Pat. No. 5,279,787 to Oltrogge discloses methods ofmanufacturing and compositions of non-toxic projectiles containingbismuth, wherein the projectiles are made of high melting point powdersmixed with molten metals of a low melting point to thereby produce asintered metal projectile. These two prior art references are herebyincorporated by reference.

[0004] The principal drawback to using bismuth alloy shot is producingit economically in commercial quantities so as to be a viablereplacement for lead shot. Unlike lead and steel, bismuth is highlycrystalline and extremely nonductile. Bismuth also has a very lowmelting temperature and expands upon cooling. These metallurgicalproperties make it difficult or impossible to economically producebismuth shot by conventional methods.

[0005] Normal shot sizes for hunting and shooting loads range from 0.008inches to 0.33 inches. (No. 9 shot to No. 4 Buckshot) Conventionalmethods of making smaller sizes of shot (i.e., No. 9 to No. 6) are thedrop method and the Bleimeister method (sometimes called the “shortdrop” method).

[0006] In the drop method, molten lead is poured through a screen at thetop of a shot tower. The “screened” lead chills and solidifies intospheres as it falls through the air before landing, typically, in a tankof cold water.

[0007] In the Bleimeister method, molten lead is pumped through a pairof arms having small orifices along their bottom surfaces. The arms arepositioned about 4 inches above the surface of almost boiling water.Droplets of molten metal fall through the small orifices in the bottomof the arms into the water and then roll along the surface of inclinedplane pine boards to form spherical beads of molten lead. The sphericalbeads of molten lead harden as they roll and then drop to the bottom ofthe water tank, cooling on the way down.

[0008] Bismuth is highly crystalline in nature and resists forming asphere. Bismuth also expands when cooled and has a high degree of heatretention, which prevents it from cooling quickly enough to be madeusing the drop method. These properties make it impossible tomanufacture large bismuth alloy shot pellets using the drop method andthe Bleimeister method. It is also not possible to manufacture lead orsteel shot greater than size No. 5 (0.12″) using either of thesemethods.

[0009] Large lead shot is conventionally made by a process that extrudeslead wire which is then flattened into an oval ribbon by a pair ofrollers. The flattened oval ribbon is run through a pair of die wheelsthat punch out spheres of the appropriate size. Round steel shot is madeby drawing a wire and snipping it into short segments using a headermachine. The header machine then grinds the short chunks of steel wireinto spheres.

[0010] Because of the nonductility of bismuth and bismuth alloys, it isnot commercially feasible to make bismuth alloys into wire. Therefore,neither the header machine process nor the ribbon tape process may beused to make bismuth shot because both processes require that thebismuth alloy first be extruded into a wire.

[0011] The shortcomings of the previously discussed methods ofmanufacturing bismuth alloy shot leads to the conclusion that one methodof manufacturing bismuth alloy shot that has a chance to produce shoteconomically for commercial use is to use high-speed die castingmachinery capable of producing large quantities of shot in a short timeframe. The manufacturing cost of bismuth shot is very critical due tothe greater cost of raw bismuth compared to lead. The cost of bismuth istypically ten times that of conventional materials such as steel andlead. Thus, any die casting process must yield a high product to wasteratio.

[0012] Analysis revealed that manufacturing costs of $5 a pound on topof raw material costs would probably result in shot shells that were tooexpensive to be commercially acceptable to purchasers. Given thepurchase price (or lease cost) of commercially available high-speed diecasters and the operating costs associated with the die casters, it wasdetermined that a minimum production level of at least a hundred poundsper hour of bismuth alloy shot had to be attained. Unfortunately, therewere no die-blocks commercially available for producing shot made frombismuth alloy. The initial die-blocks custom fabricated for theinventors using traditional die design techniques failed to produce anacceptable number of shot pellets per casting in order to attain onehundred pounds of shot pellets per hour.

[0013] For example, number 4 shot requires approximately 1600 pelletsper pound, at a rate of 100 pounds per hour, to be commercially viable.Traditional mold design techniques used to cast small parts cannotattain these numbers because they have an unacceptably high ratio ofsprue and runner material to shot pellets. For example, in most cases,approximately 70% of the metal injected into the die block forms spruesand runners to which the shot pellets are attached. These sprues andrunners are waste metal that is remelted in the melting pot andrepresent a cost of approximately $3.11 per pound of waste per casting,exclusive of any other manufacturing costs.

[0014] Conventional high speed die casters and die blocks were alsofound to be unsuitable for casting bismuth alloy shot pellets becausethe heat retention of the bismuth increased the cycle time of themachines, minimizing production rates. Also, the expansion of bismuthwhen cooled was in part responsible for slowing down the flow of thematerial through the die block.

[0015] There is therefore a need for a method of quickly andeconomically manufacturing shot made from bismuth and bismuth alloys invarious sizes.

SUMMARY OF THE INVENTION

[0016] The foregoing problems inherent in the prior art methods ofmanufacturing shot are solved by the present invention, which provides amethod of die casting bismuth alloy shot in commercial quantities at aneconomical cost.

[0017] The problems inherent in commercially available high speed diecasters and die blocks are solved by using a die block that casts anarray of tightly packed shot pellets using a minimum amount of sprue.The shot pellets in one embodiment form an array around the sprue,wherein each pellet in the pellet array touches at least two otherpellets and often four other pellets. Thus, as the molten bismuth alloyflows out of the sprue into the pellet cavities within the die block,the molten bismuth alloy flows between shot pellets thereby bypassingblockages and flowing a greater distance away from the sprue beforesolidifying. This produces a higher yield of good pellets per cast andalso allows the use of a larger die capable of producing more pelletsper cast.

[0018] A further improvement on conventional die blocks includes themachining away of approximately 0.0015 inches of material from both diefaces so as to form a narrow gap, or “fill void,” across the entire diesurface, thereby allowing a thin “flashing” to form between all pelletsin the shot pellet array. The combination of the multiple contact pointsbetween shot pellets in the array and the fill void allows the moltenbismuth alloy to flow from the common sprue to the outer limits of thedie much more quickly, before the molten bismuth alloy is able tosolidify. The fill void and multiple contact points between shot pelletssignificantly reduces the sprue needed to spread the molten bismuthalloy throughout the die, while at the same time ensuring that the dieis completely filled during each die casting. A less than complete fillresults in partially hollow shot pellets, broken shot pellets, or areduced number of pellets per cast due to empty, or partially emptycavities in the array.

[0019] After each shot pellet array is cast, the array is ejected fromthe mold and gathered into a container. The container is then dumpedinto a tumbling device containing tumbling media, such as ball bearings,in order to break up the shot pellet array, which resembles a sheet ofpellets. The tumbling pulverizes the flashing between the shot pelletsinto a fine powder. The tumbling also grinds off the small “nipples”that are formed at the contact points between the shot pellets in thearray. The tumbling process smoothens the properly formed pellets intonearly smooth spheres. Any imperfectly formed pellets or hollow pelletsare pounded flat during tumbling.

[0020] After tumbling, the shot is sifted through a sifting screen toeliminate all metal pieces that are not shot pellets, such as thesprues. Once sifted, the shot pellets are moved by a conveyor belt tothe top of a shot classifier which rolls the shot pellets down a seriesof steps set at varying angles for varying shot sizes to therebyautomatically discard all less-than-round shot pellets including theimperfectly formed and hollow pellets. The remaining shot is collectedat the bottom of the classifier and is ready for commercial usage. Theshot may be sold in bulk for reloading in the commercial marketplace orloaded into shells using conventional manufacturing methods.

[0021] The foregoing has outlined rather broadly the features andtechnical advantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand the specific embodiment disclosed may be readily utilized as a basisfor modifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWING

[0022] For a more complete understanding of the present invention,reference is now made to the following descriptions taken in conjunctionwith the accompanying drawing, in which:

[0023]FIG. 1 is a front view of a die face used in the presentinvention.

[0024]FIG. 2 is a side view of 2 die halves as used by the presentinvention.

[0025]FIG. 3 is a plan view of a portion of the shot pellet arrayproduced by the present invention.

[0026]FIG. 4 is a plan view of a portion of a shot pellet array producedby the present invention wherein the rows of shot pellets areinterlaced.

[0027]FIG. 5 is an elevational cross-sectional view of a shot pelletarray produced by the present invention, taken substantially along line5--5 of FIG. 3.

[0028]FIG. 6 is an elevational cross-sectional view of a shot pelletarray produced by the present invention, taken substantially line 6--6of FIG. 3.

[0029]FIG. 7 is a depiction of a high speed die casting machineembodying the present invention.

DETAILED DESCRIPTION

[0030] The principles of the present invention and their advantages arebest understood by referring to the illustrated embodiments depicted inFIGS. 1-7 of the drawings, in which like numbers designate like parts.

[0031]FIG. 1 depicts a die face 100 contained on a die block used toproduce an array of shot pellets in accordance with one embodiment ofthe present invention. The embodiment of the present invention shown inFIG. 1 comprises four quadrants 101-104 of hemispherical impressions 110connected to a central sprue channel 105 that is disposed along die face100. Sprue channel 105 is connected to sprue hole 220, through whichmolten bismuth alloy is injected. The molten bismuth alloy flows alongsprue channel 105 and into quadrants 104-105 of hemisphericalimpressions 110 disposed along sprue channel 105.

[0032]FIG. 2 depicts a side view of both halves of die block 200 used toproduce shot pellet arrays in accordance with the present invention.Stationary die block 205 contains sprue hole 220 and sprue channel 105b. Stationary die block 205 also contains a number of hemisphericalimpressions 110 b, each of which form one-half of a shot pellet. Movabledie block 210 is the opposing mirror-image half of die block 200 thatmates with stationary die block 205. Guideposts 215 are used to alignmovable die block 210 and stationary die block 205. Movable die block210 contains sprue channel 105 a which mates with sprue channel 105 b instationary die block 205 to thereby form sprue channel 105. Movable dieblock 210 also contains hemispherical impressions 11Oa which mate withopposing hemispherical impressions 110 b in stationary die block 205, tothereby form the shot pellets in accordance with the present invention.In the embodiment of the present invention shown in FIG. 2, a smallamount of metal has been milled from the face of stationary die block205, thereby forming flashing gap 225. In some embodiments of thepresent invention, flashing gap 225 is formed by milling the surface ofonly one die face. In other embodiments of the present invention,flashing gap 225 may be formed by milling both die faces. In eitherembodiment, the flashing gap 225 that is formed between stationary dieblock 205 and movable die block 210 will typically be approximately0.003 inches in thickness.

[0033] Additionally, in some embodiments of the present invention,either sprue channel 105 a or sprue channel 105 b may be omitted, solong as the remaining sprue channel is connected to sprue hole 220. Shotpellets may be produced by the present invention even if the spruechannel 105 is cut into only one die face and flashing gap 225 is alsocut into only one die face, so long as the hemispherical impressions 110in the die face are connected with the sprue channel 105.

[0034]FIG. 3 is an enlarged view of a shot pellet array produced by oneembodiment of the present invention. Shot pellet array 300 contains shotpellets 301-308 which are connected by vias 310, 320, 330, 340, 345, 350and 355. Shot pellets 301-308 are also interconnected by flashing 370.As molten bismuth flows through die block 200, it fills the cavitiesthat form shot pellets 301-308 and flows between shot pellets 301-308 bymeans of vias 310-355 and flashing 370.

[0035] In another embodiment of the present invention, (not shown) vias310-355 may be eliminated by packing the shot pellets 301-308 so tightlythat the shot pellet 301-308 touch one another. This may be accomplishedby positioning the center point of each hemispherical impression 110 indie face 100 sufficiently close to the center point of adjoininghemispherical impressions 110 so that the circumferences of thehemispherical impressions 110 overlap slightly. When the die blocks 205and 210 are brought together, the overlaps in the circumferences ofhemispherical impressions 110 will define holes between adjoiningspherical cavities. Forming interconnections between the shot pellets301-308 by this method allows the shot pellet 301-308 to be packed moretightly in die face 100, thereby producing a slightly higher yield ofshot pellets per casting and further reducing the “waste” material.

[0036] However, this method also requires that the separation betweenthe centers of the hemispherical impressions 110 in the die face 100 bevery precisely located in order to accurately control the diameter ofthe hole connecting adjoining shot pellets 301-308. If the hemisphericalimpressions 110 overlap by too much or by too little, the hole formedbetween the spherical cavities in the die block 200 may be too narrow toallow the molten bismuth to flow freely therebetween, or so wide that itis difficult to break the shot pellets apart. This method, if nottightly controlled, could also result in flat surfaces on the pellets.

[0037] By using via channels 310-355 as shown in FIG. 3, it is easier tocontrol the diameters of the interconnections between shot pellets301-308, although the yield of shot pellets per casting will be slightlylower.

[0038]FIG. 4 depicts an alternative embodiment to the arrangement ofshot pellet 301-308 shown in FIG. 3. In FIG. 4, shot pellets 401-408 aredisposed in interlaced rows and columns of shot pellets. This allows aslightly tighter packing of shot pellets 401-408 than may be obtainedusing the rectangular grid of shot pellets 301-308 shown in FIG. 3. Ofcourse, any grid configuration could be utilized, including oval,circular, or rectangular.

[0039] The following explanation of FIGS. 5 and 6, which illustrateelevational cross-sectional views taken substantially along line 5--5and line 6--6 through shot pellet array 300 as depicted in FIG. 3, alsoapplies to the shot pellet array 400 depicted in FIG. 4. For the purposeof simplicity, however, FIGS. 5 and 6 will be explained with referenceto the shot pellet array 300 shown in FIG. 3.

[0040]FIG. 5 illustrates elevational cross-sectional view 500 takenalong line 5--5 through shot pellets 306, 307 and 308 in FIG. 3.Cross-sectional view 500 in FIG. 3 cuts through the center lines of via345, via 355 and shot pellet 307. The two parallel dotted linestraversing the horizontal diameter of shot pellet 307 and the centers ofvia 345 and via 355 represent flashing 370, which interconnects allpellets in the shot pellet array. When via channels are cut in both diefaces in stationary die block 205 and movable die block 210, viachannels 345 and 355 will be centered on the horizontal diameters of theshot pellets 301-308. If the via channels are cut between hemisphericalimpressions 110 in only one die face, then via channels 345 and 355 willbe disposed on only one side of the horizontal diameters of the shotpellets 301-308.

[0041] Similarly, if flashing 370 is formed by milling flashing gap 225in both die faces of stationary die block 205 and movable die block 210,then flashing 370 will be centered around the horizontal diameters ofshot pellets 301-308. If, however, flashing gap 225 is milled in onlyone die face, then flashing 370 will be disposed on only one side of thehorizontal diameters of shot pellets 301-308. For purposes of furtherdiscussion, it will be assumed that the vias interconnecting the shotpellets in the shot pellet array were formed by cutting via channels inboth die faces. It will also be assumed that flashing 370 was formed bymilling flashing gaps in both die faces of die blocks 205 and 210.

[0042]FIG. 6 shows elevational cross-sectional view 600 taken along line6--6 through shot pellet array 300. Cross-sectional view 600 in FIG. 6cuts through flashing 370 and vias 340 and 350. Shown in the backgroundof cross-sectional view 600 are shot pellets 302 and 303 andinterconnecting vias 310, 320 and 330.

[0043]FIG. 7 depicts a high speed casting machine, such as a HorlaDM250, that may be used to cast shot pellets in accordance with thepresent invention. Pure bismuth or bismuth and another metal are pouredinto hopper 710 in order to produce shot pellets of pure bismuth orbismuth alloy. The bismuth and other metal, such as tin, (if a bismuthalloy is desired) are heated in furnace 715 to produce molten bismuthalloy, which is injected through tube 720 into die blocks 205 and 210.For purposes of further discussion of FIG. 7, it will be assumed that abismuth alloy is being used.

[0044] Prior to injection of the molten bismuth alloy, die blocks 205and 210 are pressed together by ram 730 which is driven by motor 725. Inone embodiment of the present invention, the bismuth alloy is heated toa temperature of approximately 600.degree. Fahrenheit. Additionally, inone embodiment of the present invention, either stationary die block 205or movable die block 210, or both, may be heated to a temperature ofapproximately 125.degree. Fahrenheit in order to slow down the rate atwhich the bismuth alloy cools as it spreads through the die block. Thishelps to ensure that the molten bismuth alloy will spread to thefarthest extremity of die face 100 before solidifying.

[0045] Furnace 715 draws approximately 6 ounces of molten bismuth alloyinto a plunger and injects the alloy at 600 p.s.i. through tube 720 intosprue hole 220 (not shown) in stationary die block 205. The moltenbismuth alloy then spreads through sprue channel 105 and into quadrants101-104 of the shot pellet array. In some embodiments of the presentinvention, quadrants 102 and 103 are connected and quadrants 101 and 104are connected to thereby form two halves on either side of sprue channel105, rather than quadrants.

[0046] The interconnections between sprue channel 105 and the first rowof shot pellets 110 connected to sprue channel 105 may be made slightlylarger than the interconnections between individual shot pellets 110.This will allow the molten bismuth alloy to flow more quickly out ofsprue channel 105 and into the first row of shot pellets 110.

[0047] After the molten bismuth alloy has been injected into the mateddie blocks 205 and 210, the molten bismuth alloy is allowed to cool fora period of approximately 5 seconds. At that point, motor 725 withdrawsram 730, thereby moving movable die block 210 away from stationary dieblock 205. At the same time, ejector pins (not shown) in stationary dieblock 205 eject the shot pellet array from stationary die block 205,causing it to fall into chute 740 and into container 745.

[0048] The entire process is controlled by control unit 750, which maybe used to vary the melting temperature in furnace 715, the heatingtemperature of die blocks 205 and/or 210, and the length of the timedelay during which the molten bismuth alloy is allowed to cool in thedie block before stationary die block 205 and movable die block 210 areseparated.

[0049] After a sufficient amount of shot pellet array has been gatheredin container 745, the shot pellet array is dumped into tumbling device760, which contains tumbling media (not shown), such as large ballbearings, which are used to break up the shot pellet array intoindividual shoe pellets.

[0050] In other embodiments of the present invention, the shot pelletarray may be moved directly from chute 740 to tumbling device 760 by anautomated device, such as a conveyor belt. The shot pellet array istumbled in tumbling device 760 for a sufficient period of time to breakapart the individual shot pellets and to smooth off the flashing 760between the individual shot pellets and to smooth away the small“nipples” formed when the vias connecting the shot pellets are broken.

[0051] The time required to complete the tumbling process varies from 10minutes to a half hour depending on the size of the shot that is beingcast. After a sufficient time period to allow the tumbling device 760 tobreak up the shot pellet array, the contents of tumbling device 760 arepoured through sifter 770 to separate the individual shot pellets fromthe tumbling media and the pieces of sprue. The shot pellets then fallinto container 780, which may contain a conveyor belt that moves theshot pellets to a classifier. As explained above, the classifierseparates the spherical shot pellets from improperly formed shotpellets, such as broken shot pellets or hollow shot pellets that wereflattened during the tumbling process.

[0052] Although the present invention and its advantages have beendescribed in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the invention as defined by the appended claims.

What is claimed is:
 1. A method for producing shot pellets, said methodcomprising: casting an array of shot pellets from a shot pellet alloymaterial, wherein each shot pellet of said array of shot pellets isconnected to at least two other shot pellets of said array of shotpellets by said shot pellet alloy material; tumbling said array of shotpellets with a tumbling media, wherein said tumbling breaks up said shotpellet array into individual shot pellets and causes connecting portionsof said shot pellet alloy material to be removed from surfaces of saidshot pellets, and wherein said tumbling media deforms improperly castshot pellets of said array of shot pellets for separation from properlycast shot pellets of said array of shot pellets.
 2. The method claim 1 ,wherein said pellet alloy material expands when transitioning from theliquid to the solid state.
 3. The method of claim 2 , wherein said shotpellet alloy material is a bismuth alloy.
 4. The method of claim 3 ,wherein said bismuth alloy includes tin.
 5. The method of claim 1 ,wherein said tumbling media includes ball bearings.
 6. The method ofclaim 1 , wherein said tumbling is continued for a time in the range offrom 10 to 30 minutes.
 7. The method of claim 1 , further comprising:poring the tumbled array of shot pellets through a sifter to separatethe individual shot pellets from said tumbling media.
 8. The method ofclaim 7 , further comprising: separating the properly cast shot pelletsfrom the improperly cast shot pellets using a classifier.
 9. The methodof claim 8 , wherein said classifier rolls the shot pellets down aseries of steps set at varying angles for varying shot sizes to therebyautomatically discard all less-than-round shot pellets including saidimproperly cast shot pellets.
 10. A system for producing shot pellets,said system comprising: means for casting an array of shot pellets froma shot pellet alloy material, wherein each shot pellet of said array ofshot pellets is connected to at least two other shot pellets of saidarray of shot pellets by said shot pellet alloy material; means fortumbling said array of shot pellets with a tumbling media, wherein saidtumbling breaks up said shot pellet array into individual shot pelletsand causes connecting portions of said shot pellet alloy material to beremoved from surfaces of said shot pellets, and wherein said tumblingmedia deforms improperly cast shot pellets of said array of shot pelletsfor separation from properly cast shot pellets of said array of shotpellets.
 11. The system claim 1 O, wherein said pellet alloy materialexpands when transitioning from the liquid to the solid state.
 12. Thesystem of claim 11 , wherein said shot pellet alloy material is abismuth alloy.
 13. The system of claim 12 , wherein said bismuth alloyincludes tin.
 14. The system of claim 10 , wherein said tumbling mediaincludes ball bearings.
 15. The system of claim 10 , wherein saidtumbling is continued for a time in the range of from 10 to 30 minutes.16. The system of claim 10 , further comprising: means for sifting thetumbled array of shot pellets to separate the individual shot pelletsfrom said tumbling media.
 17. The system of claim 16 , furthercomprising: means for classifying the properly cast shot pellets fromthe improperly cast shot pellets.
 18. The system of claim 17 , wherein aclassifier of said means for classifying rolls the shot pellets down aseries of steps set at varying angles for varying shot sizes to therebyautomatically discard all less-than-round shot pellets including saidimproperly cast shot pellets.
 19. The system of claim 10 , wherein aplurality of said shot pellets of said array of shot pellets are alsoconnected to a sprue by said shot pellet alloy material, wherein athickness of said shot pellet alloy material connecting said shotpellets to said sprue is larger than a thickness of said shot pelletalloy material connecting said shot pellets to said at least two othershot pellets of said shot pellet array.